A device is known in which a microlens array is formed such that microlenses are arranged in a two-dimensional plane, and a photoelectric conversion element is formed such that two pairs of photoelectric conversion sections are disposed at the rear side of each microlens, so as to detect the focus adjustment state of a photographic optical system in vertical and horizontal directions of an imaging screen by using the image sensor (see Patent Document 1). Also, a configuration is known in which one of the two pairs of photoelectric conversion sections are disposed at the outer side of the other of the two pairs of photoelectric conversion sections (see Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 58-24105
Patent Document 2: Japanese Unexamined Patent Application Publication No. 55-143404